Topic 6 Forensics And immunity Flashcards
1
Q
What role do microorganisms play in the decomposition of organic matter?
A
Microorganisms, such as bacteria and fungi, decompose dead organic matter into small molecules that they can respire.
This process is essential for recycling carbon back into the atmosphere.
2
Q
What gases are released when microorganisms respire small molecules during decomposition?
A
Methane (CH₄) and carbon dioxide (CO₂)
These gases are part of the carbon cycle.
3
Q
What is the significance of determining the time of death (TOD) in forensics?
A
Establishing the TOD can provide information about the circumstances of death and who was present.
It can help police and forensic scientists in their investigations.
4
Q
What is algor mortis?
A
The process by which a dead body’s temperature falls until it equals the temperature of its surroundings.
This occurs after death as metabolic reactions slow down.
5
Q
At what rate does a human body typically cool after death?
A
Around 1.5 °C to 2.0 °C per hour.
This cooling rate can be affected by environmental factors.
6
Q
What is rigor mortis?
A
The stiffening of muscles that occurs approximately 4-6 hours after death.
It begins when muscle cells are deprived of oxygen.
7
Q
What causes rigor mortis?
A
The lack of ATP due to anaerobic respiration leads to the fixation of myosin and actin bonds in muscle cells.
This results in muscle stiffness.
8
Q
How does temperature affect rigor mortis?
A
Rigor mortis occurs more quickly at higher temperatures because chemical reactions in the body are faster.
This can influence the timing of death estimations.
9
Q
What is forensic entomology?
A
The study of insects that colonize a dead body to estimate the time of death.
It often involves identifying the types of insects present.
10
Q
How can the time of death be estimated using insect life cycles?
A
By identifying the type of insect and the stage of its life cycle.
For example, blowfly larvae hatch from eggs about 24 hours after being laid.
11
Q
What factors can affect the life cycle of insects on a decomposing body?
A
Drugs, humidity, oxygen, and temperature.
Higher temperatures can speed up metabolic rates and shorten life cycles.
12
Q
What is the extent of decomposition in the first few days after death?
A
Cells and tissues are being broken down by bacteria and enzymes.
This process begins immediately after death.
13
Q
What happens to the body after a few weeks of decomposition?
A
Tissues begin to liquefy and seep out into the area around the body.
This is part of the natural decomposition process.
14
Q
What is the final stage of decomposition?
A
Only a skeleton remains after a few months to a few years.
Eventually, the skeleton disintegrates over decades to centuries.
15
Q
What is succession in the context of a dead body?
A
The changing types of organisms found on a dead body over time.
This process helps forensic scientists estimate the time of death.
16
Q
What conditions favor the initial colonization of a dead body?
A
Immediately after death, conditions are most favorable for bacteria.
This is followed by flies and their larvae.
17
Q
Fill in the blank: The body begins to bloat due to gases produced during decomposition, such as ______.
A
[methane]
This bloating is a sign of microbial activity.
18
Q
True or False: The stage of succession on a dead body is affected by its location.
A
True
For example, a body sealed away will not be colonized by insects.
19
Q
What is a DNA profile?
A
A fingerprint of an organism’s DNA
Everyone’s DNA is unique except for identical twins.
20
Q
What are the four bases that make up nucleotides in DNA?
A
- A
- T
- C
- G
These bases pair as A with T and C with G.
21
Q
What is the purpose of DNA profiling?
A
To identify people and determine genetic relationships
This includes relationships between humans, animals, and plants.
22
Q
What is the first step in creating a DNA profile?
A
A DNA sample is obtained from the organism
This can be collected from bodily fluids or tissues.
23
Q
What process is used to amplify DNA for profiling?
A
Polymerase Chain Reaction (PCR)
PCR involves multiple stages to create many copies of DNA.
24
Q
What components are included in a PCR reaction mixture?
A
- DNA sample
- Free nucleotides
- Primers
- DNA polymerase
Primers are short DNA sequences that initiate replication.
25
At what temperature does the DNA mixture need to be heated to break hydrogen bonds?
95 °C
## Footnote
This step denatures the DNA strands.
26
What is the purpose of cooling the mixture to between 50 and 65 °C during PCR?
To allow primers to bind (anneal) to the strands
## Footnote
This is essential for the subsequent DNA synthesis.
27
What temperature is used for DNA polymerase to synthesize new strands?
72 °C
## Footnote
This temperature is optimal for the enzyme's activity.
28
How does the amount of DNA change with each PCR cycle?
It doubles each cycle
## Footnote
E.g., 1st cycle = 2 fragments, 2nd cycle = 4 fragments, etc.
29
What is the purpose of adding a fluorescent tag to DNA?
To visualize the DNA fragments under UV light
## Footnote
This helps in identifying and comparing DNA profiles.
30
How does gel electrophoresis separate DNA fragments?
By length
## Footnote
DNA moves towards the anode due to its negative charge.
31
What happens to shorter DNA fragments during gel electrophoresis?
They move faster and travel further
## Footnote
This results in separation according to length.
32
What do DNA profiles look like when viewed under UV light?
They appear as bands
## Footnote
The pattern of bands can be compared between profiles.
33
What is one application of DNA profiling in forensic science?
To link suspects to crime scenes
## Footnote
DNA from crime scene samples is compared to suspects' DNA.
34
What is the first step a forensic scientist takes when collecting DNA from a crime scene?
Isolate DNA from collected samples
## Footnote
This includes samples from blood, semen, skin cells, etc.
35
What is the final step in comparing DNA profiles in forensic science?
Compare the PCR products on an electrophoresis gel
## Footnote
Matching profiles indicate a link to the crime scene.
36
What do we inherit from our parents in terms of DNA?
Roughly half comes from each parent.
37
What does it indicate if more bands on DNA profiles match?
The more closely-related (genetically similar) those two people are.
38
How can DNA profiling determine the biological father of a child?
By comparing DNA profiles; lots of matching bands suggest the individual is the child's father.
39
What is one application of DNA profiling in animals and plants?
To prevent inbreeding, which causes health, productivity, and reproductive problems.
40
What is inbreeding and why is it problematic?
Inbreeding decreases the gene pool, leading to an increased risk of genetic disorders.
41
What is the relationship between DNA profile similarity and relatedness?
The more closely-related two individuals are, the more similar their DNA profiles will be.
42
What is the first step in carrying out gel electrophoresis?
Add a gel tray to a gel box (or tank).
43
What type of gel is commonly used for electrophoresis?
Agarose gel.
44
How are wells created in the gel for electrophoresis?
A row of wells is created at one end of the gel.
45
What is the purpose of the buffer solution in gel electrophoresis?
To cover the surface of the gel and facilitate the movement of DNA fragments.
46
What is the role of loading dye in DNA sample preparation?
It helps the samples to sink to the bottom of the wells and makes them easier to see.
47
How should DNA samples be added to the gel wells?
Using a micropipette, ensuring the tip is just above the opening of the well.
48
What happens when the power supply is turned on during electrophoresis?
An electrical current is passed through the gel, causing DNA fragments to separate according to length.
49
How long should the gel run during electrophoresis?
For about 30 minutes or until the dye is about 2 cm from the end of the gel.
50
What is the purpose of staining the DNA fragments after electrophoresis?
To make the bands of different DNA fragments visible.
51
How is the length of a DNA fragment measured?
In bases, e.g., ATCC = 4 bases or base pairs.
52
What does PCR stand for?
Polymerase Chain Reaction.
53
True or False: Identical twins have the same DNA profile.
True.
54
Briefly describe the procedure to separate DNA fragments by electrophoresis.
Prepare agarose gel, load DNA samples into wells, apply electric current, and visualize the results.
55
What is the significance of DNA profiling in forensic science?
It can provide conclusive proof of identity in criminal investigations.
56
Fill in the blank: The length of 1000 bases is referred to as _____ .
one kilobase (1 kb).
57
What type of cells are bacteria?
Bacteria are single-celled prokaryotic organisms
## Footnote
Prokaryotic means they have no nucleus.
58
What is the size of most bacteria?
Most bacteria are only a few micrometers (um) long, e.g. the TB bacterium is about 1 um.
59
What are the main components of bacterial cells?
Bacterial cells have:
* Plasma membrane
* Cytoplasm
* Ribosomes
* Cell wall
* Flagella
* Pili
* Capsule
* DNA (bacterial chromosome and plasmids)
60
What is the function of the flagellum in bacteria?
The flagellum is a long, hair-like structure that rotates to make the bacterium move.
61
What is the primary function of ribosomes in bacteria?
Ribosomes produce proteins from mRNA.
62
What is murein?
Murein is a component of the bacterial cell wall.
63
What are pili in bacteria used for?
Pili help bacteria stick to other cells and can be used in gene transfer.
64
What is the purpose of a bacterial capsule?
The capsule helps to protect the bacterium from attack by cells of the immune system.
65
How is bacterial DNA structured?
The DNA of a bacterium floats free in the cytoplasm and is typically in one long, circular, coiled-up strand called a bacterial chromosome.
66
What are plasmids?
Plasmids are small loops of DNA that aren't part of the bacterial chromosome.
67
How do viruses differ from bacteria?
Viruses are not cells; they are nucleic acids surrounded by protein and are smaller than bacteria.
68
What components do viruses lack that bacteria have?
Viruses lack plasma membranes, cytoplasm, and ribosomes.
69
What is the function of the capsid in viruses?
The capsid is the protein coat around the core of a virus.
70
What is an envelope in the context of viruses?
An envelope is an extra outer layer that some viruses have, stolen from the cell membrane of a previous host cell.
71
What are attachment proteins in viruses used for?
Attachment proteins allow the virus to cling on to a suitable host cell.
72
Define a pathogen.
A pathogen is any organism that causes disease.
73
What are infectious diseases?
Diseases caused by pathogens.
74
What type of microorganisms can be pathogenic?
Pathogenic microorganisms include some bacteria, some fungi, and all viruses.
75
What is HIV's primary method of replication?
HIV replicates inside the T helper cells of its host.
76
What is reverse transcriptase?
An enzyme carried by HIV that is used to make complementary DNA from viral RNA.
77
What happens during the latency period of HIV infection?
HIV replication drops to a lower level, and the infected person doesn't experience symptoms.
78
What condition does HIV eventually lead to?
HIV infection eventually leads to acquired immune deficiency syndrome (AIDS).
79
What defines AIDS?
AIDS is a condition where the immune system deteriorates and eventually fails.
80
What are opportunistic infections?
Infections that develop in people with a weakened immune system, typically seen in AIDS patients.
81
List the initial symptoms of AIDS.
Initial symptoms of AIDS include:
* Minor infections of mucous membranes
* Recurring respiratory infections
82
What serious infections can develop in late-stage AIDS?
Serious infections include:
* Toxoplasmosis of the brain
* Candidiasis of the respiratory system
83
True or False: The length of time between HIV infection and the development of AIDS is the same for everyone.
False
84
What factors affect the progression of HIV to AIDS?
Factors include:
* Existing infections
* Strain of HIV
* Age
* Access to health care
85
What bacterium causes tuberculosis (TB)?
Mycobacterium tuberculosis
## Footnote
Mycobacterium tuberculosis is a slow-growing bacterium that primarily affects the lungs.
86
How is tuberculosis (TB) contracted?
Infection occurs when tiny droplets containing the bacteria are inhaled into the lungs
## Footnote
These droplets can be released into the air when an infected person coughs or sneezes.
87
What type of white blood cell engulfs Mycobacterium tuberculosis?
Phagocyte
## Footnote
Phagocytes are a type of immune cell responsible for engulfing and digesting pathogens.
88
What happens to Mycobacterium tuberculosis inside phagocytes?
The bacteria survive and replicate
## Footnote
Mycobacterium tuberculosis can evade digestion and replicate within phagocytes.
89
What structures in the lungs seal off infected phagocytes?
Tubercles
## Footnote
Tubercles are small, rounded structures formed by the immune response to contain the infection.
90
What is a likely consequence of dormant Mycobacterium tuberculosis being reactivated?
It can cause tuberculosis (TB)
## Footnote
Reactivation is more likely in individuals with weakened immune systems.
91
What are the initial symptoms of tuberculosis?
Fever, general weakness, and severe coughing
## Footnote
These symptoms are caused by inflammation of the lungs.
92
What can untreated tuberculosis lead to?
Respiratory failure and organ failure
## Footnote
Left untreated, TB can cause severe complications that may lead to death.
93
Through which routes can pathogens enter the body?
Through cuts in the skin, digestive system, respiratory system, and other mucosal surfaces
## Footnote
Each route poses a risk for different types of infections.
94
What role does stomach acid play in preventing infection?
It kills most pathogens
## Footnote
Stomach acid is a significant barrier to pathogens ingested with food or drink.
95
What is the function of skin flora?
They compete with pathogens for nutrients and space
## Footnote
Skin flora helps limit the number of pathogens that can colonize the skin.
96
What enzyme is found in secretions from mucosal surfaces that helps kill bacteria?
Lysozyme
## Footnote
Lysozyme damages bacterial cell walls, leading to their destruction.
97
What triggers the non-specific immune response?
Recognition of foreign antigens on the surface of a pathogen
## Footnote
This response is immediate and not specific to any particular pathogen.
98
What are the signs of inflammation at the site of infection?
Redness, warmth, swelling, and pain
## Footnote
Inflammation is a key part of the immune response to infection.
99
What process increases blood flow to the site of infection?
Vasodilation
## Footnote
Vasodilation is triggered by molecules released during the immune response.
100
Fill in the blank: The immune system cells can then start to ______ the pathogen.
destroy
## Footnote
This is the ultimate goal of the immune response at the site of infection.
101
What are interferons?
Proteins produced by infected cells to prevent virus spread.
## Footnote
Interferons play a crucial role in the immune response against viral infections.
102
How do interferons prevent viral replication?
By inhibiting the production of viral proteins.
## Footnote
This action limits the ability of viruses to reproduce within host cells.
103
What role do interferons play in the immune response?
They activate cells involved in the specific immune response and other mechanisms of the non-specific immune response.
## Footnote
This includes promoting inflammation to recruit immune cells.
104
What is phagocytosis?
The process where a phagocyte engulfs and digests pathogens.
## Footnote
Phagocytes are essential for the non-specific immune response.
105
What happens when a phagocyte encounters a pathogen?
It recognizes the antigens, engulfs the pathogen, and forms a phagocytic vacuole.
## Footnote
This vacuole contains the pathogen for digestion.
106
What is the function of lysosomes in phagocytosis?
They fuse with phagocytic vacuoles and contain enzymes that break down pathogens.
## Footnote
Lysozymes are a key component in the destruction of engulfed pathogens.
107
What are antigen-presenting cells?
Cells that present pathogen antigens on their surface to activate other immune cells.
## Footnote
Phagocytes, such as macrophages, serve this role.
108
State four ways in which pathogens can enter the body.
1. Respiratory tract
2. Digestive tract
3. Skin
4. Urogenital tract
109
State two barriers that prevent infection.
1. Skin
2. Mucous membranes
110
What are antigens?
Substances that can trigger an immune response.
## Footnote
Antigens are typically found on the surface of pathogens.
111
Describe two ways in which interferons prevent viruses from spreading to uninfected cells.
1. Inhibit viral protein production
2. Activate immune cells to kill infected cells
112
How is inflammation triggered at the site of infection?
By the release of signaling molecules that increase blood flow and attract immune cells.
113
How does inflammation aid the immune response?
It recruits immune cells to the site of infection and increases the permeability of blood vessels.
114
What is the role of T cells in the immune response?
They recognize antigens and activate other immune cells.
## Footnote
T cells include helper, killer, and memory cells.
115
What happens when a T cell binds to a complementary antigen?
It gets activated and divides to produce clones.
## Footnote
This process amplifies the immune response.
116
What are the different types of T cells and their functions?
* T helper cells - activate B cells and other immune cells
* T killer cells - kill pathogen-infected cells
* T memory cells - provide long-term immunity
117
What are B cells covered with?
Proteins called antibodies.
118
What do antibodies do?
They bind to antigens to form antigen-antibody complexes.
## Footnote
This interaction marks pathogens for destruction or neutralization.
119
What occurs when a B cell's antibody meets a complementary antigen?
The B cell is activated and divides into plasma cells and memory cells.
120
What are plasma cells?
Clones of B cells that secrete antibodies specific to an antigen
## Footnote
Plasma cells are identical to B cells.
121
What do antibodies consist of?
Four polypeptide chains: two heavy chains and two light chains
## Footnote
Each chain has a variable region and a constant region.
122
What is the role of the variable region in antibodies?
Forms the antigen binding sites and is complementary to a particular antigen
## Footnote
The variable regions differ between antibodies.
123
What is the function of the hinge region in antibodies?
Allows flexibility when the antibody binds to the antigen
124
What do the constant regions of antibodies do?
Allow binding to receptors on immune system cells, e.g., phagocytes
## Footnote
The constant region is the same in all antibodies.
125
What holds the polypeptide chains of antibodies together?
Disulfide bridges
126
How do antibodies help to clear infections?
By agglutination, neutralizing toxins, and preventing pathogen binding
## Footnote
Each antibody can bind to two pathogens, clumping them together for phagocytosis.
127
What is agglutination?
The clumping together of pathogens by antibodies
128
What is the effect of antibodies binding to toxins?
Neutralizes the toxins by preventing them from affecting human cells
129
How do antibodies prevent pathogens from binding to human cells?
By blocking the cell surface receptors that pathogens need to attach to host cells
130
What are the two forms of antibodies?
Membrane-bound and secreted
## Footnote
Membrane-bound antibodies have an extra section of protein that anchors them to the B cell membrane.
131
What is the process called that copies a gene into mRNA?
Transcription
132
What are introns?
Sections of DNA that do not code for amino acids
133
What are exons?
Sections of DNA that do code for amino acids
134
What is pre-mRNA?
mRNA strands containing both introns and exons
135
What is splicing?
The process of removing introns and joining exons to form mRNA strands
136
What is alternative splicing?
The process where certain exons are removed along with introns to form different mRNA strands
137
What percentage of human genes undergo alternative splicing?
About 95%
138
How can one gene give rise to more than one protein?
By modifying the mRNA before it's translated into protein through alternative splicing
139
What cells do activated B cells divide into?
Plasma cells and memory B cells
140
True or False: Antibodies can only be found in a secreted form.
False
141
What is the role of macrophages in T cell activation?
Engulf pathogens and present antigens to T cells
142
What structures are found on the surface of T cells that bind to antigens?
T cell receptors
143
What activates the immune system when a pathogen enters the body for the first time?
The antigens on the pathogen's surface activate the immune system.
144
What are the two components of the primary immune response?
* Non-specific immune response
* Specific immune response
145
Why is the primary response slow?
There aren't many B cells that can make the antibody needed to bind to the antigen.
146
What happens after the body produces enough of the right antibody during the primary response?
The infected person will show symptoms of the disease.
147
What are memory cells and what role do they play in immunity?
Memory cells remain in the body for a long time and help the immune system respond quicker during a second exposure.
148
What do B memory cells record?
The specific antibodies needed to bind to the antigen.
149
What is the secondary immune response?
The immune response that occurs when the same pathogen enters the body again, producing a quicker and stronger response.
150
What do memory cells divide into during the secondary response?
* Plasma cells (B effector cells)
* Cells that produce the right antibody to the antigen
151
What are the two types of active immunity?
* Natural - immunity after catching a disease
* Artificial - immunity after vaccination
152
What is passive immunity?
Immunity obtained from being given antibodies made by a different organism.
153
What are the two types of passive immunity?
* Natural - antibodies received from the mother
* Artificial - injected with antibodies
154
How do vaccines provide immunity?
Vaccines contain antigens that stimulate the primary immune response without causing the disease.
155
What is one method by which some vaccines work?
Some vaccines use mRNA to instruct cells to produce antigens.
156
What is antigenic variation?
The process that creates different strains of pathogens due to mutations in antigen proteins.
157
What is one evasion mechanism of HIV?
HIV kills immune system cells it infects, reducing the number of cells available to detect HIV.
158
How does HIV's high mutation rate affect the immune response?
It results in new strains of the virus, requiring a primary response each time a new strain appears.
159
How does Mycobacterium tuberculosis evade the immune system?
It produces substances that prevent the lysosome from fusing with the phagocytic vacuole, allowing it to multiply undetected.
160
Fill in the blank: The production of memory cells gives _______.
[immunity]
161
True or False: Active immunity is acquired only through vaccinations.
False
162
Describe the role of B memory cells in the secondary response.
B memory cells rapidly produce the specific antibodies needed when re-exposed to the same antigen.
163
State two differences between active and passive immunity.
* Active immunity involves the individual's immune system producing antibodies
* Passive immunity involves receiving antibodies from another organism
164
Describe how a vaccine gives immunity to a pathogen.
A vaccine contains antigens that stimulate the primary immune response without causing disease.
165
Describe one way in which Mycobacterium tuberculosis evades the immune system.
It prevents lysosome fusion with phagocytic vacuoles, allowing it to multiply undetected.
166
What are antibiotics?
Chemicals that kill or inhibit the growth of microorganisms
## Footnote
Antibiotics are used to treat bacterial infections.
167
What are bacteriocidal antibiotics?
Antibiotics that kill bacteria
## Footnote
Examples include penicillin and amoxicillin.
168
What are bacteriostatic antibiotics?
Antibiotics that prevent bacteria from growing
## Footnote
They inhibit bacterial metabolism without killing the bacteria.
169
How do antibiotics work?
By inhibiting bacterial metabolism
## Footnote
They interfere with growth and life processes of the cell.
170
What is one way antibiotics inhibit bacterial growth?
By inhibiting enzymes needed to make chemical bonds in bacterial cell walls
## Footnote
This results in weakened cell walls that can lead to cell death.
171
How do antibiotics affect protein production in bacteria?
They bind to bacterial ribosomes, inhibiting protein synthesis
## Footnote
Without protein production, bacteria can't carry out essential metabolic processes.
172
What is a clear zone (inhibition zone)?
A clear patch in the lawn of bacteria where growth is inhibited by an antibiotic
## Footnote
The size of the clear zone indicates the effectiveness of the antibiotic.
173
What is the importance of aseptic techniques in antibiotic investigations?
To prevent contamination of bacterial cultures with unwanted microorganisms
## Footnote
Contamination can affect results and pose health risks.
174
What are some aseptic techniques?
Regular disinfection of surfaces, using sterile equipment, working near a Bunsen burner
## Footnote
These techniques minimize contamination in bacterial cultures.
175
What are hospital-acquired infections (HAIs)?
Infections that patients acquire during their hospital stay
## Footnote
They can be caused by antibiotic-resistant bacteria.
176
What can contribute to the development of antibiotic resistance in bacteria?
Overprescribing antibiotics and improper use by patients
## Footnote
This can lead to serious health problems and difficulty in treating infections.
177
List some codes of practice to prevent antibiotic resistance.
* Avoid prescribing antibiotics for minor infections
* Use narrow-spectrum antibiotics
* Rotate the use of different antibiotics
* Ensure patients complete their prescribed course
## Footnote
These practices help reduce the likelihood of bacterial resistance.
178
True or False: Antibiotics are effective against viral infections.
False
## Footnote
Antibiotics are designed to target bacteria, not viruses.
179
Fill in the blank: The size of a clear zone indicates how well an antibiotic __________.
works against bacteria
## Footnote
A larger clear zone means greater inhibition of bacterial growth.
180
Name two processes in a bacterial cell that antibiotics can inhibit.
* Enzyme activity in cell wall synthesis
* Protein synthesis
## Footnote
These processes are essential for bacterial growth and survival.
181
What should doctors avoid when prescribing antibiotics?
Prescribing them for viral infections and for preventive measures
## Footnote
This helps to minimize the development of antibiotic resistance.
182
What happens to bacteria when they are exposed to antibiotics?
They may evolve resistance and survive despite treatment
## Footnote
This can lead to more severe infections and complications.
